This invention relates to an engine spark plug which incorporates one or more weakened structural zones designed to rupture under operating conditions of extreme cylinder pressure, thereby providing a large air passage out of the cylinder to quickly vent liquid and air from the cylinder and avert conditions that could cause internal engine damage.
The four-stroke cycle internal combustion engine has long been vulnerable to the often disastrous effects of ingesting water into the combustion chamber during engine operation. Water which passes through the induction system (air box, filter, carburetor/airflow sensor, intake manifold) of an internal combustion engine enters the cylinder during the intake stroke. During the next compression stroke sufficient quantities of this water, which is effectively incompressible, will cause an increase in cylinder pressure well above ordinary operating pressures, until one or more engine components fail. Typical component failures include bent, broken, or holed pistons, piston pins, connecting rods, crankshafts, rod or crank bearings, cracked cylinder heads, cracked blocks or blown head gaskets. The result of such failures is either to vent the compressed cylinder contents to a region of lower pressure, deform the cylinder, or halt the piston's upward travel. This phenomenon is known as hydrostatic lock, hydrolock, or hydraulic lock, all referring to the condition in which liquids ingested into a running engine cause the engine instantly to stop, often accompanied by one or more of the aforementioned failures.
Certain applications of internal combustion engines are more susceptible to hydrolock than others. Off-road vehicles, such as 4 wheel drive trucks, all terrain vehicles and motorcycles, watercraft, and even passenger cars passing through standing water or flood waters are at risk. Hydrolock related repairs to the engines of such vehicles are enormously expensive, often costing thousands of dollars to repair. It would therefore be advantageous to design an engine or engine component which releases trapped liquids before hydrolock related damage occurs.
A similar, but generally less catastrophic condition, is the incidence of detonation in which, for any one of a number of reasons, the fuel-air mixture in the cylinder fails to ignite or burn properly and causes excessive pressure in the cylinder, often accompanied by a distinctive "ping."
Combustion in ordinary internal combustion engine is characterized by a flame front propagating roughly hemispherically away from the ignition source (the spark). As the flame front propagates, it produces a continuing increase in cylinder pressure, effectively driving the piston downward and producing torque on the crankshaft. Detonation is the phenomenon of spontaneous combustion of the fuel-air mixture, generating a nearly instantaneous shock (pressure) wave throughout the cylinder and precluding the continual generation of pressure associated with a normally propagating flame front. Detonation may occur silently or audibly, and may be severe or mild. Severe detonation may melt, crack, or hole pistons and other top cylinder or crankcase components in a matter of seconds.
Earlier inventions provide for the avoidance of damage due to detonation by employing a poppet-style valve to react to the pressure wave of ensuing detonation. However, while a poppet valve may be effective in attenuating the magnitude of the shock wave which accompanies detonation, it does nothing to remedy the condition. At the end of each detonating cycle the cylinder purges and replenishes itself to repeat the phenomenon the next cycle. The thermomechanical shock to the cylinder and cylinder components accompanying the deployment of the detonation "prevention" valve or spark plug is attenuated to the degree that imminent component failure is temporarily avoided. However, the onset and, more importantly to the engine tuner, the cause of detonation have not been identified nor addressed. In multi-cylinder applications, the spark plug of the detonating cylinder does not readily reveal itself so that investigation into detonation in that particular cylinder may be specifically investigated. Given that detonation may be silent, and is capable of imparting severe damage in a short period of time in a highly tuned engine (such as a racing application), it is important that detonation be discovered, and its cause remedied, as early as possible.
Both hydrolock and detonation are deleterious to engine operation, and both are inexpensively remediable if discovered and treated prior to engine failure. The spark plug of this invention is designed to avert engine failure caused by hydrolock or detonation by venting excessive pressure out of an affected cylinder before the pressure becomes so great as to cause other engine components to fail.
The two-stroke cycle internal combustion engine presents a decreased potential to hydrolock. The decreased potential is chiefly due to the entry of the fuel-air mixture into the crankcase prior to admission into the cylinder. The compression ratio of the mixture in the crankcase (the primary chamber) is far lower than the compression ration in the cylinder (the secondary chamber). This permits a comparatively large amount of water to enter a two-stroke cycle engine without immediate damage. Water in the crankcase does not enter the cylinder immediately, as the transfer port tends to take air from the top of the crankcase rather than water from the bottom (assuming a cylinder-up orientation during the stroke in which water was ingested). The water-laden fuel-air mixture is unlikely to fire, leading to engine shut down due to lack of ignition and combustion. Nevertheless, there is a danger that hydrolock will be severe enough to cause the failure of engine components, requiring major repairs to restore the engine to an operable condition.
The present invention is a modification of a typical internal combustion engine spark plug, which employs all of the technology and features of ordinary spark plugs in terms of application, heat ranges, radio interference suppression, and functions identically to ordinary plugs under normal operating conditions. Upon the development of excessive cylinder pressures, however, the spark plug permanently deforms or disintegrates, generating a passage suitably large to permit the expulsion of gasses or liquids to prevent engine damage. Upon deformation or disintegration the spark plug will no longer form an airtight seal, and replacement of the spark plug must be performed.